I did the bzr branch to get the current sources to play with. But when I tried to down load the required additional frameworks from http://sbooth.org/Play/#download I only got a link pointing to a non-existing .tar.gz file. Is there a new download that works?

When I double-click on the error, it opens up Interface Builder and asks me to locate the missing plugin. the only thing I manage to point it at is ThirdParty/RBSplitView/build/Debug/RBSplitView.framework/Versions/A/RBSplitView, but then something funny happens. It makes IB crash with an assertion error:

Assertion Message: Two plug-ins (net.brockerhoff.RBsplitView.IBPlugin and net.brockerhoff.RBSplitView.IBPlugin) both integrate a class description for the class RBSplitSubview. The primary definition for the class should only come from one plug-in; the other plug-in should be declaring a category. Declaring a category is accomplished by omitting the super class from classdescription file.